We are investigating excited-state charge transfer and symmetry breaking in twisted acceptor-donor-acceptor (A-D-A) systems synthesized by the Gidron group at the University of Jerusalem. The figures depict time-resolved IR spectra in the −C≡C− stretching region after photoexcitation of the molecules. In non-polar solvents, a single -C≡C- band is observed in both cases, pointing to a symmetric distribution of the excitation over both D-A sides of the molecules. As solvent polarity is increased, a new band appears around 2120 cm–1. It is characteristic of a pure dipolar state, revealing occurrence of excited-state symmetry breaking (ESSB). For the twisted molecule (n=4), this process is already observed in a medium polar solvent (THF). The solvent polarity has to be increased for ESSB to take place in the non-distorted molecule (n=8).
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Contact:
Eric Vauthey
Physical Chemistry Department - Sciences II - University of Geneva
30, Quai Ernest Ansermet - CH-1211 Geneva 4 (Switzerland)
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